Optical output spdif interface. Connecting and setting up SPDIF-HDMI audio on a computer. Placing components on the board

958 type II in the international standard IEC-60958). It is a collection of low-level protocol and hardware implementation specifications that describe the transmission of digital audio between various components of audio equipment. When describing S/PDIF, it is necessary to describe both the physical part (that is, how the signal is transmitted and why) and the software part (that is, the protocol used).

S/P-DIF is the consumer version of the standard known as AES/EBU; has slight protocol differences and requires less expensive hardware.

Applications

S/PDIF was originally used in players (and DVD players that play CDs), and then became a common way to connect and transmit audio in other audio components, such as MiniDisc players and sound cards for personal computers. It has also gained popularity in car audio, where the former clutter of multiple wires can be replaced by a single fiber optic cable that is resistant to electrical interference.

Another application of the S/PDIF interface is in the transmission of digital surround sound as defined by the IEC 61937 standard. This mode is used to connect the output of a DVD player to the input of a home theater AV receiver that supports Dolby Digital or Digital Theater System (DTS) surround formats. sound.

S/PDIF (Sony*/Philips* Digital Interface) is an audio interface format that supports the transmission of digital audio signals from one device to another without conversion to analog, thereby avoiding degradation of sound quality.

For SPDIF, 192-bit words are divided into 12 words of 16 bits each. The first 6 bits of the first word are the control code; the meaning of these bits is shown in the table:

Other

S/PDIF is defined by the international standard IEC 60958-3.

Notes

Bibliography

J. Watkinson The Art of Digital Audio, Third Edition, Focal Press, 2001

Wikimedia Foundation. 2010.

Manufacturers of modern TV models have been able to ensure that the reproduced audio signal is clear and loud. But not all owners are satisfied with the standard sound and there is a need to output sound to an external media device, for example, a home theater.

S/PDIF is an international standard for digital audio transmission. Data transfer is realized through several cables and connectors. It was first used in audio players. But the technology began to develop and the S/PDIF mode appeared on home theaters, car radios, personal computers and modern TV models.

What is S/PDIF on TV

A digital or optical S/PDIF connector on the TV is required for output and further transmission of audio signals in the appropriate format. If a movie or program is broadcast in HD quality on the TV receiver and the device supports 5.1 format, then sound will be output from the TV in digital or optical format. On modern TV models it is usually presented in the form of a Toslink or coaxial connector.

S/PDIF Standard Types

S/PDIF technology has two types of signal transmission: coaxial and optical.

Coaxial output. Although this audio transmission option is becoming a thing of the past, some Internet and cable providers still use it. This connector is also present on home theaters, video and audio players and car radios. It provides digital quality audio transmission between digital equipment. To make this possible, you need to connect the devices to each other using an appropriate coaxial cable. The digital connector is capable of transmitting multi-channel or stereo sound without loss of audio signal quality. This connection option is inexpensive. But if there is an electromagnetic field nearby, the sound quality drops significantly.
Toslink. At the moment, it is through this connector that the TV is connected to external devices for sound transmission. This is an optical interface capable of reproducing a signal that is not subject to external influences. To connect the media system to a TV receiver using the optical output, a fiber optic cable is required. If high-quality wire is used, the connection between the equipment will be reliable and the sound will be ideal. Currently produced televisions and media systems are equipped with an optical interface. When choosing, you must take into account the characteristics of the connected devices, as well as whether there are appropriate connectors. The connection and setup procedure itself is quite simple. You need to connect all devices using a cable, and in the sound settings of the TV you need to find the “Speakers” item and select “External speakers”.

What is S/PDIF for?

The Sony/Philips S/PDIF interface is very common. This is a standard channel for transmitting digital audio between equipment. It is very compact and is the only technology for transmitting sound that is completely resistant to external influences and various interferences, which allows for high-quality sound.

REFERENCE! S/PDIF mode perfectly reproduces stereo surround sound, allowing you to fully enjoy audio or video files.

This connector can be found on televisions, media devices, and personal computer motherboards. Its sole purpose is to transmit a high-quality digital signal between various digital equipment, excluding the mandatory procedure of converting a digital signal to analog.

When connecting various media devices using this interface, you can fully enjoy 5.1 sound. It is especially relevant when it is not possible to connect equipment using a cable and an HDMI connector.

This technology is very popular in televisions. Connection and settings take very little time, but in return the user receives high-quality sound.

Digital interfaces have long been pushing aside their analog ancestors. Middle-class audio systems use sound encoded in one of many standards as a signal source. This could be banal PCM for stereo sound or the Dolby family of standards for their multi-channel relatives. But today we will not talk about encoding methods, but about how exactly the signal is transmitted. There are only two options - optical and coaxial cable. The optics guarantee complete electrical isolation, the coaxial cable is easy to connect.

For ten years now, almost every motherboard has been equipped with an optical digital output S/PDIF (aka TOSLINK). But if you look at the back panel you can’t always find it. What's the catch? The manufacturer does not want to install another connector on the rear panel and increase the cost of the board by installing an optical module or a socket for a coaxial cable. If you open the documentation for the motherboard, you will find a typical set of four contacts similar to a socket for connecting a speaker.

On the same page there is a branded strip with coaxial and optical outputs. Sometimes there are also optical inputs, but the author of the article only read about this on the Internet. Finding an original plank can turn into a non-trivial task - the price at foreign auctions is about $10, excluding delivery. A quick search on Russian-speaking forums finds only requests for its purchase and advice to buy a sound card with the appropriate socket instead.

According to the specification, the signal level on the motherboard is TTL; we can only guess about the load capacity of the SPDIFOUT output. The same documentation recommends loading it with an LED with a current-limiting resistor - this will be the cheapest connection. I didn’t dare try this option first for two reasons - I felt sorry for the board and the urgent need to plug a standard optical cable somewhere. Later, I nevertheless assembled an emitter follower on one transistor and connected an LED. The interface glowed cheerfully with a red LED, but the optical cable attached to it did not produce sound. The same documentation recommended choosing an ultra-bright LED with a wavelength of 660 nanometers. Perhaps none of the LEDs used were suitable.

The next step is to connect the recommended TOTX173 optical module. The price and availability in online stores are again not encouraging - a little less than the same ten dollars and long delivery. So it's time to look for a donor. After going through the electronics dump at home, we were able to identify only one victim; it turned out to be a Playstation 2, a gift from employees for their last birthday. No hand was raised against the vandalism of the legendary console. At a regional online auction, a Samsung DVD Recorder was caught for the same sacred $10 without delivery. Photos will follow.

S/PDIF on the victim looked like this

Since a search using the code on the case (T2002H7) did not yield anything, the device had to be turned on in a disassembled state to make sure that a five-volt power supply and a TTL signal level were used.

There are only three contacts, the common one is easily identified, the power is connected directly to the signed 5V plug, leaving the information output connected through a 220 Ohm resistor. Here's a close-up of our newfound module.

All that remains is to connect to the motherboard and assemble it all in the form of a bracket. We connect the common pin to common, power to power, and SPDIFOUT through a 220 Ohm resistor to data. We assemble a PC bracket from a piece of a breadboard and a burnt-out network card, this is what I did.

We install it in the case.

More than two weeks have passed since the installation - everything works perfectly. By ear, of course, the difference is within the limits of the sensations given by psychology. But if there is acoustics that understands optics, why not use a connection made by yourself. In the comments, it would be interesting to hear an opinion about the possible difference in the sound of such an optical output and that obtained from a mid-price range sound card.

After assembly, I made my way to the nearest appliance repair shop. It was there that we should immediately look for a donor - they have a sufficient number of burnt-out DVD players, for about a dollar per fee. For those who want to repeat the design, this will be useful.

USB cable 120cm long

Optical cable 1M long

The ends are covered with rubber protective caps.

The connector is standard SPDIF with beveled corners.
Many of you, like me, have sometimes seen it on TV and some computers, but have never used it, so it will be interesting to find out what kind of beast it is.

There is an optical fiber inside, if light is applied to one end, it can be removed from the other end.

And finally, the converter itself is a metal box with connectors on both sides.

On one side there are inputs: power and digital audio, either via an optical Toslink cable like ours, or via a coaxial one.

On the other side, there are outputs: 3.5mm headphone output, two RCA tulips and a power indicator, red and quite vigorous.

The dimensions of the converter are small: 5.5cm*6cm*2cm
But it is quite weighty thanks to the metal body: 82g

The converter is easy to disassemble, just unscrew the screw.

And then two more and you're done:

The work at the back is a little sloppy, the soldering is ugly in places, and the flux has not been washed off in some places.
I'll give you close-up photos:
http://s19.postimg.org/42zggy8tv/audio_converter_19.jpg
http://s19.postimg.org/bmsjj020j/audio_converter_20.jpg
http://s19.postimg.org/o05dpwroz/audio_converter_21.jpg
http://s19.postimg.org/fkft8eotv/audio_converter_22.jpg

Well, let's connect.
The connection is incredibly simple, insert the necessary wires where necessary and power it from the USB of the TV itself.
The indicator is eye-catching, like a mini flashlight.

It’s better to turn it somewhere back into the wall or completely seal it, since at least when the TV is turned off, it’s also turned off.
In the TV settings, in the sound section, you can choose where to output the sound; on Samsung, the fastest way to get there is through the quick settings button.

If the audio output is selected as in the screenshot, then the sound in the TV itself no longer comes, and when we try to adjust the volume it will write that we have tuned in to external speakers and now we must adjust the sound with their remote control.

You don’t have to switch the sound to external ones, they always play as soon as they are plugged in, then both external and internal speakers will play at the same time, and in many cases there will be an echo due to the time it takes to convert digital to analog, a kind of hall effect.
You can mute the built-in speakers or reduce their volume to zero so that the muted speaker icon does not appear on the side.
But when watching especially multi-channel films, it is better to use both speakers; the TV transmits mid-frequencies well - speech, music. the center acts as a sub and provides special effects.
During operation, the converter practically does not heat up.

I don't have a professional microphone, so I did my best with a regular camcorder to convey to you the difference in sound between the built-in speakers and external ones.
In reality the difference is even higher than in the video.
You will need bass headphones or speakers to hear the difference; you are unlikely to distinguish anything in laptop speakers or desktop plastic tweeters.

That's all, thank you all for your attention.

Every self-respecting music lover who builds a PC-based audio system using an external DAC is forced to answer a seemingly insignificant, but fundamental question in practice. USB or SPDIF connection? Let's try to dot the i's once and for all!

This marvelous, fantastic for that time brainchild of scientific progress of the 1980s, SPDIF, still remains relevant. Originally a professional switching standard in digital recording studios, it has gained ground in home systems. So what is the secret of this “optics”?

The truth is that there is no secret here. We all know that transmitting data at the speed of light virtually eliminates the possibility of direct competition. This standard makes it possible to almost completely eliminate such an undesirable phenomenon as jitter from digital signal processing. Jitter occurs when there is even minimal frequency mismatch between the digital signal source and its receiver. That is, if the source produces a signal with a higher frequency than the receiver is capable of receiving and processing, then jitter arises on the latter’s side and, accordingly, the need to resample the signal so that it can be processed. SPDIF is completely free of such drawbacks. After all, its sampling frequency is set by the source. The receiver is capable of processing a signal with almost any frequency available to the source. Therefore, modern DACs connected via SPDIF are capable of processing a digital audio signal even with 24/192 characteristics without downsampling.

An example of a reference signal transmission via “optics”

The USB Audio v.1 format cannot boast of this. Alas, receiver devices working with this standard are often not capable of processing a signal with characteristics higher than 16/48. And even though the documentation for the standard says 24/96, but in practice even the Windows operating system forcibly (!) lowers the values for the outgoing signal to 16/48 when an audio device created on the basis of this protocol is connected to a PC. The thing is that the protocol, developed and certified in 1998, is exclusively synchronous. What does it mean? In practice, this means that before starting to transmit a digital signal, the source and receiver “agree” with each other about the frequency with which this transmission will occur. This frequency remains the same throughout the transmission. That is, during the same period of time, due to forced frequency equalization, completely different amounts of data can be transmitted. The receiver can handle processing a certain volume without problems, but in the next millisecond a new volume of data, exceeding the previous one, can make it “strain” very much. And this leads to the inevitable loss of some of the details of the audio track, distortion and other undesirable consequences. That is, there is no need to talk about Hi-Fi anymore.

The same signal performed by USB Audio 1.0. Sad sight

USB Audio v.2 was intended to correct the situation. It already has an asynchronous operating mode, which in itself almost completely eliminates jitter. The standard, introduced in 2009, however, requires USB 2.0 or 3.0 for its successful operation. And, of course, it is not compatible with previously released DACs. However, high-quality sound requires sacrifices :). In fact, the reliability of the signal transmitted via USB Audio 2.0 is not inferior to that of SPDIF/Toslink. Thus, DACs and external sound cards released after 2009 and supporting USB Audio 2.0 both in hardware and at the driver level are capable of providing sound quality indistinguishable from “optics”. To be fair, it should be noted that there are no drivers that provide support for USB Audio v.2 right out of the box, even in Windows 10. And the task of developing them falls on the shoulders of manufacturers of external sound cards and DACs. And they, in turn, cope with it quite successfully.

USB Audio 2.0 Async works wonders

The choice of connection method is now made only on the basis of personal preferences, and not the technical superiority of one format over another. P Therefore, the statement that “optics” is better than USB is today a myth, although quite widespread. See you soon!

P.S. Illustrations obtained under ideal conditions and on reference equipment are taken from the resource materials